1. Field of the invention
The present invention relates to a valve operating system for internal combustion engines, comprising a free cam follower which is disposed between first and second drive cam followers operatively connected to engine valves and which is capable of becoming free relative to the engine valves, first and second guide holes respectively provided in the first and second drive cam followers with their axes corresponding to each other, the guide holes being opened to the free cam follower, a double open-ended guide hole provided in the free cam follower in correspondence to the axes of the first and second guide holes, a first change-over pin axially slidably received in the first guide hole and adapted to be fitted into the guide hole, a second change-over pin axially slidably received in the guide hole with one end thereof abutting against the first change-over pin, the second change-over pin being adapted to be fitted into the second guide hole, and a restricting pin axially slidably received in the second guide hole while being spring-biased toward the second change-over pin, with one end thereof abutting against the other end of the second change-over pin.
2. Description of the prior art
Such system is conventionally known, for example, from Japanese Patent Application Laid-open No. 19911/86 and the like.
In such valve operating system, the first and second drive cam followers as well as the free cam follower are connected by fitting of the first change-over pin into the free cam follower and fitting of the second change-over pin into the second drive cam follower. In order to prevent impossibility of connection due to striking of the first and second change-over pins against sides of the free cam follower and the second drive cam follower during such connecting operation, the accuracy of inside diameters of the first and second guide holes and the accuracy of outside diameters of the pins have been controlled to .mu.m. Even if the single part accuracies of the cam followers and the pins are improved, however, dimensional tolerances between the parts mutually associated are accumulated on assembling and as a result, the operation of connection by the first and second change-over pins may be impossible in some cases.